From the Magazine

Taking the Life Out of Titan

Many planetary geologists say Titan is alive. Radar images from the Cassini spacecraft show what look like volcanoes thought to spew icy "lavas" and pump methane into Titan's atmosphere. But a group of planetary physicists report this week that Titan appears to be encased in a shell of rock-hard ice tens of kilometers thick—perhaps too rigid to allow ice magma to rise from the depths. If they are right, the "volcanoes" are something else entirely, Titan is geologically dead, and the moon's store of atmospheric methane—the source of the rains that cut its canyons and fill its lakes—may be dwindling. Titan may be drying out.